3-4 clutchpacks toast?
03-03-2013, 08:40 AM
#1
3-4 clutchpacks toast? went to cecil dragway yesterday and on the 8th pass right when the car shifted from 2nd to 3rd the the car felt like it was in neutral. so i let off and just coasted to the end of the track adn turn off. so i left the shifter in D and 1-2 shifted fine so did 2-3 and then when it went to shift from 3-4 the rpm felt rose rather quickly as if the converter didnt engage and the car doesnt have any/alot of power to move. now if i leave the shifter in 3rd the converter locks like normal. so does this sound like the 3-4 clutchpack fried scenario? trans is stock w/approx 95k miles but the motor is cammed with bolt-ons and the rear is a 12bolt w/3.73.
03-03-2013, 11:15 AM
#4
Moderator
The "shifted from 2nd to 3rd the the car felt like it was in neutral" is usually a good indicator that the 3-4 clutch is toast.
But then you say "1-2 shifted fine so did 2-3". Hmmm strange.
If it slips in [D4] but not in [D3] is often an indicator that the forward sprag is slipping; but I'm not sure you said that.
You also say that the 3-4 shift is nearly always slipping badly; if 3rd is good, but 4th is bad indicates a problem with the servo, 4th accumulator or valve body.
(Internally 4th gear is a combination of 2nd and 3rd gear.)
There is either some inconsistency here or a rare combination of problems.
All of this might be consistent with very low pump pressure.
I would suggest going to a local trans shop and having them put a pressure gauge on it and a scanner that can force it through all the gears with the wheels up.
I'm not an expert, but I don't see how a bad shift solenoid could give these exact symptoms. (Perhaps similar, but not exact according to your description.) The trans shop scan/test would point out a bad solenoid. The trans shop will probably want to drop the pan and examine the oil for burnt friction crud.
But then you say "1-2 shifted fine so did 2-3". Hmmm strange.
If it slips in [D4] but not in [D3] is often an indicator that the forward sprag is slipping; but I'm not sure you said that.
You also say that the 3-4 shift is nearly always slipping badly; if 3rd is good, but 4th is bad indicates a problem with the servo, 4th accumulator or valve body.
(Internally 4th gear is a combination of 2nd and 3rd gear.)
There is either some inconsistency here or a rare combination of problems.
All of this might be consistent with very low pump pressure.
I would suggest going to a local trans shop and having them put a pressure gauge on it and a scanner that can force it through all the gears with the wheels up.
I'm not an expert, but I don't see how a bad shift solenoid could give these exact symptoms. (Perhaps similar, but not exact according to your description.) The trans shop scan/test would point out a bad solenoid. The trans shop will probably want to drop the pan and examine the oil for burnt friction crud.
03-03-2013, 09:11 PM
#5
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mrvedit you gave me info on an earlier thread and I'm shopping rebuilt 4L60E's and new stall as I type this!
Anyway reading this thread the symptom sounds similar. I spent the day at a car meet and driving around with really NO issues. Only happens when I really hammer the gas and my 2nd to 3rd does that same thing, feels like neutral, bangs rev limiter until lazily shifting into 3rd. But if I drive 'normal' it shifts okay. Fst100, do you also lose 3rd only when you are racing it?
not to venture too far off point, but I see Jakes Performance really pushes the 4L80E and is this tranny a bolt on upgrade option for our Fbodies? Or is there a lot of work, extras or tuning involved. I will prob never be above 550rwhp and I'm thinking a rebuilt 4L60E would be fine for me, but Jake really talks them up on his site.
Anyway reading this thread the symptom sounds similar. I spent the day at a car meet and driving around with really NO issues. Only happens when I really hammer the gas and my 2nd to 3rd does that same thing, feels like neutral, bangs rev limiter until lazily shifting into 3rd. But if I drive 'normal' it shifts okay. Fst100, do you also lose 3rd only when you are racing it?
not to venture too far off point, but I see Jakes Performance really pushes the 4L80E and is this tranny a bolt on upgrade option for our Fbodies? Or is there a lot of work, extras or tuning involved. I will prob never be above 550rwhp and I'm thinking a rebuilt 4L60E would be fine for me, but Jake really talks them up on his site.
03-03-2013, 10:15 PM
#6
Moderator
RJDio: Your Q about 4L80E is off-topic here. Search for "4L80E swap" to find a wealth of info. In short, the swap to a 4L80E is not trivial - pound out tunnel a bit, new crossmember, new converter ($$$), harness and PCM changes, etc. I'm sure Jake can build you a 4L60E to handle 550rwhp; you might ask him to build you one with the new Sonnax Smart-Tech input drum; it would bump the price by $650 or so, but give a much more durable 3-4 clutch.
03-04-2013, 05:56 AM
#7
Fst100, do you also lose 3rd only when you are racing it?
not to venture too far off point, but I see Jakes Performance really pushes the 4L80E and is this tranny a bolt on upgrade option for our Fbodies? Or is there a lot of work, extras or tuning involved. I will prob never be above 550rwhp and I'm thinking a rebuilt 4L60E would be fine for me, but Jake really talks them up on his site.
not to venture too far off point, but I see Jakes Performance really pushes the 4L80E and is this tranny a bolt on upgrade option for our Fbodies? Or is there a lot of work, extras or tuning involved. I will prob never be above 550rwhp and I'm thinking a rebuilt 4L60E would be fine for me, but Jake really talks them up on his site.
. also my rear passenger wheel weight fell off on one of my last couple runs and the car was shaking and vibrating like crazy as well as i think the rear is hitting the swaybar or some bar that's a few centimeters behind it when i apply throttle. doesnt do it when theres no throttle though
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03-04-2013, 07:43 AM
#8
TECH Junkie
Forward sprag or solenoids are your most likely issues as listed above. If you have a multimeter and some mechanical skill you can check the solenoids. Do a search on ATSG website or similar reliable source and check out the solenoid resistance with the multi. To do this you'll need to drop the pan so while your at it check the condition of the fluid and look at the magnet in the bottom of the pan to see if it has collected much clutch material or other metals. This may help you decide if it really is the clutches or an alternate problem.
03-04-2013, 07:52 AM
#9
well, at this point might as well just get the trans built to handle the power as well as my plans in the future to go FI. i was expecting the trans to fail on me sooner or later. i could tell by how none of my commanded shift mph and RPMs were sticking as the trans was shifting 500-600RPMs above the commanded and the mph were 10mph higher as well. for example on the 2-3 upshift:
commanded RPM 5800 and MPH 58
actual RPM 6550 and MPH 69
and the commanded MPH i imagine is under the commanded RPM but not by alot to cause the pcm to go bonkers or anything cause it didnt hit the rev limiter. also the shift pressure were upped to 96psi and shift desired time 0.150 and i slightly tweaked the FMC lower in the 150-175*F trans temp at the 90-96psi from 154 to like 146 to quicken the shifts.
commanded RPM 5800 and MPH 58
actual RPM 6550 and MPH 69
and the commanded MPH i imagine is under the commanded RPM but not by alot to cause the pcm to go bonkers or anything cause it didnt hit the rev limiter. also the shift pressure were upped to 96psi and shift desired time 0.150 and i slightly tweaked the FMC lower in the 150-175*F trans temp at the 90-96psi from 154 to like 146 to quicken the shifts.
03-04-2013, 04:24 PM
#10
Moderator
Sounds like you have a good handle on the trans tuning. Shifting 750 rpm over the commanded value sounds very high; makes me wonder if a solenoid is sticking or you have very low line pressure. You might try replacing the shift solenoids "just for the fun of it". You can test the solenoids with an ohm meter, but they can also stick and/or their filters can fill with crud.
Not trying to correct you, but setting a shift value of "96" doesn't set 96psi, it sets the maximum value, which is actually more in the 175-225 psi range, depending upon the boost valve and pressure regulator spring. Joecar describes it in post #7 in this thread:
https://ls1tech.com/forums/automatic...d-density.html
I would still recommend hooking a pressure gauge up as it might help know what to look for when the trans is rebuilt. A pressure gauge is only $50 on ebay and will be useful later when you are experimenting with the tuning software. The gauge has a long hose and you can attach it to your outside side mirror. Fun and educational.
Not trying to correct you, but setting a shift value of "96" doesn't set 96psi, it sets the maximum value, which is actually more in the 175-225 psi range, depending upon the boost valve and pressure regulator spring. Joecar describes it in post #7 in this thread:
https://ls1tech.com/forums/automatic...d-density.html
I would still recommend hooking a pressure gauge up as it might help know what to look for when the trans is rebuilt. A pressure gauge is only $50 on ebay and will be useful later when you are experimenting with the tuning software. The gauge has a long hose and you can attach it to your outside side mirror. Fun and educational.
03-06-2013, 12:41 PM
#12
Moderator
No, the case has a pressure "port" on the drivers side. A 11mm or 7/16" wrench removes it. IIRC it has a 1/8" pipe tread.
If you don't have a gauge, search ebay for "transmission pressure gauge". I like the "ATD 5550" model, but anything 300 or 400psi with a long hose should be fine.
If you don't have a gauge, search ebay for "transmission pressure gauge". I like the "ATD 5550" model, but anything 300 or 400psi with a long hose should be fine.
